Cerebral ischemia is the result of insufficient oxygen supply in the cellular context of brain, for the metabolic needs. This continuous jugular oximetry (hemoglobin oxygen saturation in the jugular buld SJV02) is a reliable index of the balance between supply and consumption of oxygen by the corebral tissue, specially when this balance is subject to continues alterations. We studied the shifts in oxygen saturation of hemoglobin in the mixed venous blood of jugular bulb with the purpose of early detection and prevention of cerebral ischemia. Material-Method In 17 patients ASA III, IV, who underwent carotid artery surgery, a catheterisation of the ipsilateral internal jugular vein was carried out until the jugular bulb and the oxygen saturation was monitored. Moreover samples of mixed venous and arterial blood were taken to measure the difference in oxygen saturation at several phases (before surgery, during carotid clamping, at the end of operation) or during shifts in arterial pressure. Results Despite the oxygen saturation of arterial blood was maintained stable at 98-99% along all surgical procedure, a desaturation of mixed venous blood from 5 to 30% was observed during clamping of carotid artery as well as a decrease of SJV02 from 15 to 55% during decrease of blood pressure >30%, as a reflexion of the decrease of the cerebral blood flow. After the removal of clamps the SJVOz was observed to increase from 5 to 35%. Conclusions The continuous jugular bulb oximetry is a usefull monitoring of the cerebral blood flow in order to recognize early ischemia during carotid artery surgery and to perform surgical and anesthesiological therapeutic intventions.